1. Field of the Invention
This invention relates generally to medical instruments. More particularly, this invention relates to an electrocautery probe which has an electrode of adjustable shape and/or size. The invention finds particular application in endometrial ablation, prostatic ablation, and other electrocautery procedures.
2. State of the Art
Endometrial ablation is an alternative procedure to hysterectomy for women with menorrhagia (abnormal or excessive uterine bleeding). In the past, various methods of ablation, including cryosurgery and laser surgery, have been used. More recently, electrocautery techniques have also been used. Endometrial ablation by electrocautery is usually accomplished with a resectoscope and a coagulation electrode mounted on the distal end of an electrocautery probe. The resectoscope includes a telescope for viewing the interior of the uterus, a handle assembly commonly referred to as the working element, and an outer sheath. The working element is generally capable of sliding the probe with a distally mounted electrode axially through the telescope. The outer sheath is placed into the uterus prior to introducing the other elements of the resectoscope.
The actual endometrial ablation procedure involves applying a cauterizing current to the electrode and moving the electrode slowly over the entire endometrium (uterine lining) while viewing through the scope. Thermal energy is applied to the endometrial lining of the uterus by the electrode so that the endometrium is destroyed by cauterization and subsequently scars. In order to effect complete destruction of the endometrium, the electrode is moved in a systematic manner, generally beginning at the Fallopian tube ostia (mouth), proceeding to the fundus (above the uterine tubes), and continuing on the anterior, posterior, and lateral uterine walls down to the internal os of the cervix. It is well known, however, that the uterine cavity has acute corners (the cornua and tubulo-interstitial areas) as shown by reference 12 in FIG. 1 and that a relatively small electrode must be used to effectively cauterize these portions of the endometrium. Other portions of the uterus, however, are relatively broad (14 and 16 in FIG. 1) and the use of a small electrode in these areas is tedious and time consuming.
Known electrodes for use in resectoscopes are available in many different shapes and sizes. U.S. Pat. No. 4,917,082 to Grossiet al., for example, discloses several embodiments of a "Resectoscope Electrode" including a coagulating electrode, a knife electrode, a punctate electrode, and a roller electrode, among others. Electrodes for use with resectoscopes are also widely available from Olsen Electrosurgical, Inc., Concord, Calif. They are available as blades, needles, balls, loops, spear tips, flexible wires, semicircular wires, hooks, spatulas and blunt tips.
Recently, the generally preferred electrode for use in endometrial ablation is the roller (often referred to as "rollerbar" or "roller ball") electrode depicted in prior art FIGS. 2a-2c. Such roller ball electrodes are available from Richard Wolf Medical Instruments Corp., Rosemont, Ill. or from Olympus Corp., Lake Success, N.Y. The roller bar 22 or roller ball 24 is approximately 2.5 mm long (e.g., 2.5 mm in diameter for the ball) and, as shown in FIGS. 2a-2c, is mounted on the distal end of an electrocautery probe 26. The distal ball or bar is supplied with a cauterizing current through conductors 28, 30 in the probe and is rolled across the endometrial surface methodically until all areas of the endometrium have been cauterized. Because of its small size, the ball or bar fits easily into the acute corners of the uterus. Its relatively small size, however, also renders it inefficient when used in the other portions of the uterus.
While it is possible to change from one electrode having a first size to another electrode having a second size during the ablation procedure, the changing of electrodes adds time to the procedure, increases the chance that the entire endometrium will not be properly ablated, and requires that a plurality of tools which are typically disposed of after use be utilized. Moreover, it has not been the general practice to change from one electrode to another during the ablation procedure. Thus, by using such a small electrode throughout the uterus, the ablation procedure takes longer and the chance of missing one or more portions of the endometrium is enhanced. Similar problems exist in other electrocautery procedures where an electrode of one shape or size is necessary for part of the procedure but is inefficient or inapplicable for another part of the procedure.
Co-owned U.S. Pat. No. 5,354,296 to Turkel discloses variable morphology electrodes, solving many of the problems associated with previous electrodes for the ablation procedure. As used herein, the term "morphology" refers to the shape and/or size of the electrode. The variable morphology electrodes vary in length and width to reach the various areas of the uterus with greater efficiency. The electrodes can be designed from volute spring portions, a plurality of cylinder elements, a springy wire mounted with beads, a plurality of loops, a band with tapering width and other shapes. However, while the disclosed electrodes of variable morphology can effectively change size, each electrode is generally limited to a specific shape which it can assume. In addition the electrodes lack the ability to have their shapes precisely controlled.